Centrifugal clutches are rpm-actuated clutches having radially movable centrifugal weights mounted on the drive end. Under the influence of the centrifugal force, the centrifugal weights transmit a specific torque friction tight to the output end of the centrifugal clutch with the required contact force. After reaching a limit rpm, an automatic coupling takes place so that a load free startup of the drive motors is possible. Centrifugal clutches are advantageous for rapidly running drive motors such as internal combustion engines and make possible a high starting torque for accelerating large masses in relationship to the drive power so that the drive motor does not have to be designed for short-term high starting power. Furthermore, the centrifugal clutches protect the drive motors from overload and decouple the load in the low rpm range, for example, in idle, for example, in the case where the centrifugal clutch is used in a work apparatus, such as a motor-driven chain saw. Here, the load would be the saw chain.
U.S. Pat. No. 4,106,605 discloses a centrifugal clutch wherein the centrifugal weights each have an arcuately-shaped clutch shoe and are pivotally held on a carrier disc at the output end of the centrifugal clutch. The pivot journalling of the centrifugal weights is achieved via respective bearing bolts which are mounted on the carrier disc at equal spacings from each other so as to be parallel to a rotational axis of the carrier disc. When the carrier disc is driven in rotation, the centrifugal weights pivot under the action of the centrifugal force about their respective pivot bolts and the arcuately-shaped pole shoes carry out a radial movement.
At the output end of the centrifugal clutch, a clutch drum is mounted coaxially to the carrier disc and surrounds the clutch shoes. The clutch shoes are radially movable by the centrifugal force against the return force of a coiled tension spring and can be pressed against the inner wall surface of the clutch drum. The centrifugal force exceeds the return force of the tension spring above a specific rpm range by an amount which corresponds to the application force of the clutch shoes required for the friction-tight entrainment of the clutch drum.
Intense wear occurs during operation of the known centrifugal clutch especially for frequent coupling operations. The material wear in the bearing area of the centrifugal weights leads to deteriorated operation of the centrifugal clutch.